This invention relates to what are known as "swimming rolls" [a trademark of Eduard Kuesters] in general and more particularly to an improved sealing arrangement for such rolls, which minimizes friction.
The rolls which are known as "swimming rolls" consist of a stationary core and a hollow roll or cylinder surrounding the stationary core with a spacing therefrom and rotatable thereabout. Seals are provided at the ends of the roll between the core and the hollow cylinder. Longitudinal seals are also provided along the core on both sides thereof. These seal the space between the core and the inside of the hollow cylinder so as to form a longitudinal chamber situated on the working side of the roll and which is filled with pressure liquid. On each side of the core one of the respective longitudinal seals is disposed in a longitudinal slot formed in the core, and can be pushed out of the slot against the inside of the hollow roll by the pressure of a pressure liquid in the chamber formed by the longitudinal seals.
In "swimming rolls" of this type, the longitudinal seals must rest against the inner circumference of the revolving hollow cylinder with a certain amount of pressure in order to insure the necessary sealing against the liquid pressure in the longitudinal chamber, which pressure may be several atmospheres. In the design described in U.S. Pat. No. 2,908,964 a longitudinal notch on the core is, engaged by a strip-like seal closing the side of the longitudinal chamber. The strip-like seal is inclined and has its outer edge resting against the inside circumference of the hollow roll, the seal extending radially between the core and hollow roll. Contact pressure is generated by the pressure of the liquid acting on the oblique side of the seal or by means of a spring provided for this purpose. The seal, which rests under a certain amount of pressure against the inner circumference of the rotating hollow roll, generates a certain amount of friction. This friction, while unimportant at lower rotative speeds, can no longer be neglected when considering the total power required when running at higher speeds. Such high speeds, using such a roll, are common, for example, in the manufacture or the further processing of paper webs, e.g., process which operate at 1000 m/min and more.
Another sealing arrangement for "swimming rolls," is described in German Pat. No. 2,025,777. The longitudinal seal in this case is a strip shaped bar piston which is fitted into the longitudinal slot. Pressure liquid is supplied through a line leading to the bottom of the longitudinal slot. A portion of the pressure liquid passes through fine transversal canals in the ledge-like bar piston and leaves in the vicinity of the sealing surface thereof which rests against the inside of the hollow cylinder.
Although it is the intent that a continuous film should develop in this manner between the bar piston and the passing inner wall of the hollow roll, such is only achieved in an imperfect manner in practice. This is true particularly on that side of the contact area of the bar piston which is opposite the running direction of the hollow roll. Thus, even with the design of German Pat. No. 2,025,777 friction must be expected. And, once again, a certain portion of the total power required for the drive is wasted in overcoming this friction.